Figure 6
From: Single-particle properties of topological Wannier excitons in bismuth chalcogenide nanosheets
Excitonic dispersion relation for the Coulomb potential in the trivial regime. Here the different colors simply label the principal quantum number n. Up to numerical error, at \(\varvec{Q} = \varvec{0}\) every state has a degeneracy \(g_{n} = 4(2n + 1)\), consistent with the fact that there are four exciton families each having angular momentum \(m \in \{-n, \dots , 0, \dots , n\}\). The binding energies at the origin follow the hydrogenic Rydberg series \(\Delta _{n} \propto \big (n + \frac{1}{2}\big )^{-2}\). This plot has been obtained by using the same parameters for the underlying single-particle model but changing the sign of \(B_{2}\), which produces a zero Chern number for the electrons and holes (see the “Methods” section).
